Vehicle traffic monitoring typically involves collecting traffic data from vehicles traveling on a road and analyzing the collected traffic data to learn about vehicle traffic patterns. For example, vehicles traveling past a data acquisition site may be counted for use in determining a total traffic flow volume at the data acquisition site during the period of counting. Additionally, or alternatively, instantaneous speed of vehicles may be monitored to determine traffic flow speed. Each such analysis typically involves aggregating the information collected, for example, from a selected geographic area or time, and processing the aggregated information, such as by averaging, to generate measures of traffic flow. These measures are then used, for example, to predict traffic patterns, or to evaluate the adequacy of traffic infrastructure. For example, a count of vehicles traveling through a selected intersection may be used to determine whether a traffic control device is needed at the intersection, and if so, what type of traffic control device.
Vehicle traffic data collection for use in vehicle traffic analysis is an integral part of a traffic monitoring process, because without adequate and reliable data, no valid conclusions may be obtained. To enable data collection, permanently installed sensor devices and systems, including those embedded in the roadway, have been implemented to detect vehicle traffic on the roadway at the location of the sensor device. Existing devices installed for other purposes, such as cell phone transceiver devices and toll collection devices installed along roadways, also have been used to collect data of vehicle traffic, as have portable sensor devices.